1. Field of the Invention
The present invention relates to a camera having a motor-driven zoom lens.
2. Description of Related Art
In a motor-driven zoom lens, zooming is effected by a telephoto switch and a wide-angle switch. Furthermore, a motor-driven zoom lens camera has been developed that has one, or more than one, special photographing mode (which will hereinafter be referred to as a "control zoom mode"). Such control zoom modes includes a constant image magnification mode in which the size of a main object to be photographed, such as a human figure, is kept constant in a film plane (i.e., the field of view of a finder) even if the main object moves; a zooming mode during exposure (which will hereinafter be referred to as a mid-exposure zoom mode) in which zooming is effected during exposure; and a preset zoom mode in which a focal length is changed from an optional focal length to a preset focal length.
In a known motor-driven zoom lens having more than one control zoom mode, as mentioned above, there are various switches, such as a selection switch, for selecting the control zoom modes, a changing switch for changing the control zoom modes, and a changing switch for changing a normal power zoom mode and a selected control zoom mode, etc. Such switches make the operation and construction of a camera complicated and increase the possibility of a mistake in the operation thereof.
Furthermore, in the constant image magnification mode, a photographer generally directs the camera to the main object to determine a composition and then adjusts the zooming lens so that an automatic focus adjusting operation (AF operation) is effected. Consequently, the control unit in a camera body automatically performs an arithmetic operation to determine the necessary magnification in accordance with the object distance and the focal length. These data (focal length, object distance, magnification, etc.) are set or stored in a memory of the control unit. Thereafter, the camera performs the AF operation in accordance with the main object and the control zooming to maintain constant the image magnification.
However, it is sometimes necessary for a photographer to modify the set or stored data. Accordingly, it is necessary to have a simple mechanism which can easily reset, modify and release the set or stored data.
Furthermore, in the case where a picture is taken in the control zoom mode, or the zooming is manually effected by a photographer, he or she may wish to return the focal length to a specific preset value after a picture is taken or during the zooming.